US scientists map genes of microbes in healthy individuals
By Julie Steenhuysen ,Reuters
June 15, 2012, 12:11 am TWN
CHICAGO -- U.S. scientists have analyzed 5,000 samples taken from swabs and scrapings of 250 volunteers and developed the first genetic reference map of nearly all of the microbes inhabiting healthy humans.
Like the mapping of the human genome more than a decade ago, this five-year, US$173 million census of the microbes — including bacteria, viruses and fungi — that inhabit healthy humans will be used as a reference by scientists the world over as they carry out research on human disease.
Researchers sampled up to 18 sites on participants' bodies and looked at everything from saliva to blood, skin and stool.
“This is a whole new way of looking at human biology and human disease, and it's awe-inspiring. It offers incredible new opportunities,” Dr. Phillip Tarr of Washington University School of Medicine in St. Louis, which was one of 200 U.S. scientists who took part in the effort, known as the Human Microbiome Project.
Physicians and researchers have long known that humans share their bodies with trillions of microorganisms, Dr. Eric Green, director of the National Human Genome Research Institute, one of the National Institutes of Health that backed the research, told a news briefing.
Prior estimates suggest there are 10 bacterial cells for every single human cell in the body, but because they are so small, microbial cells make up just 1 to 3 percent of our bodies' mass. In a 200-pound adult, that is 2 to 6 pounds of bacteria, Green said.
“Most of the time, humans live in harmony with our microbial hosts, but sometimes that harmony breaks down, resulting in disease,” Green said.
Understanding what makes up a normal microbiome will help doctors better understand the changes that occur when people become sick, he said.
Presented in two papers in the journal Nature and 12 papers in Public Library of Science journals known as PLoS, the researchers found that humans play host to as many as 10,000 different microbial species.
Some of the microbes found in healthy people are known to cause nasty illnesses, yet they were peacefully coexisting with an abundance of other beneficial microorganisms in this newly defined human microbiome.